Philips Semiconductors Product specification
SA602ADouble-balanced mixer and oscillator
1997 Nov 07
3
BLOCK DIAGRAM
8765
4321
OSCILLATOR
VOLTAGE
REGULATOR
GROUND
V
CC
SR00069
Figure 2. Block Diagram
AC/DC ELECTRICAL CHARACTERISTICS
V
CC
= +6V, T
A
= 25°C; unless otherwise stated.
LIMITS
SYMBOL PARAMETER TEST CONDITIONS SA602A UNITS
MIN TYP MAX
V
CC
Power supply voltage range 4.5 8.0 V
DC current drain 2.4 2.8 mA
f
IN
Input signal frequency 500 MHz
f
OSC
Oscillator frequency 200 MHz
Noise figure at 45MHz 5.0 5.5 dB
Third-order intercept point
RF
IN
= -45dBm: f
1
= 45.0MHz
f
2
= 45.06MHz
-13 -15 dBm
Conversion gain at 45MHz 14 17 dB
R
IN
RF input resistance 1.5 kΩ
C
IN
RF input capacitance 3 3.5 pF
Mixer output resistance (Pin 4 or 5) 1.5 kΩ
DESCRIPTION OF OPERATION
The SA602A is a Gilbert cell, an oscillator/buffer, and a temperature
compensated bias network as shown in the equivalent circuit. The
Gilbert cell is a differential amplifier (Pins 1 and 2) which drives a
balanced switching cell. The differential input stage provides gain
and determines the noise figure and signal handling performance of
the system.
The SA602A is designed for optimum low power performance.
When used with the SA604 as a 45MHz cellular radio second IF and
demodulator, the SA602A is capable of receiving -119dBm signals
with a 12dB S/N ratio. Third-order intercept is typically -13dBm (that
is approximately +5dBm output intercept because of the RF gain).
The system designer must be cognizant of this large signal
limitation. When designing LANs or other closed systems where
transmission levels are high, and small-signal or signal-to-noise
issues are not critical, the input to the SA602A should be
appropriately scaled.
Besides excellent low power performance well into VHF, the
SA602A is designed to be flexible. The input, RF mixer output and
oscillator ports can support a variety of configurations provided the
designer understands certain constraints, which will be explained
here.
The RF inputs (Pins 1 and 2) are biased internally. They are
symmetrical. The equivalent AC input impedance is approximately
1.5k || 3pF through 50MHz. Pins 1 and 2 can be used
interchangeably, but they should not be DC biased externally.
Figure 5 shows three typical input configurations.
The mixer outputs (Pins 4 and 5) are also internally biased. Each
output is connected to the internal positive supply by a 1.5kΩ
resistor. This permits direct output termination yet allows for
balanced output as well. Figure 6 shows three single ended output
configurations and a balanced output.
